In recent years the production of therapeutic polypeptides has steadily increased and it is likely that therapeutic polypeptides will become the biggest group of therapeutics available for the treatment of various diseases in the near future. The impact of therapeutic polypeptides emerges from their specificity, such as specific target recognition and/or binding function.
Cell cultures are used in fermentative processes to produce substances and in particular polypeptides. A distinction is made between processes in which the cell cultures are genetically unmodified and form their own metabolic products and processes in which the organisms are genetically modified in such a manner that they either produce a larger amount of their own substances such as polypeptides or produce foreign substances. The organisms producing the substances are supplied with a nutrient medium which guarantees the survival of the organisms and enables the production of the desired target compound. Numerous culture media are known for these purposes which enable an optimal cultivation of the specific host.
The use of a chemically defined minimal growth medium in the cultivation of a recombinant cell for the recombinant production of therapeutic polypeptides is advantageous. It enables easy development of downstream processing and purification of the produced therapeutic polypeptide, provides for a robust productions process due to minimized raw material differences and reduces costs of goods.
A chemically defined minimal growth medium does not comprise free amino acids and it is required to use prototrophic cell lines which have intact metabolic pathways to produce the required amino acids from the available components of the chemically defined minimal growth medium.
When, for example, E. coli is used as host cell line generally wild-type strains, such as MG1655, W3110 or BL21, are employed. These strains show good growth characteristics but inferior product titer.
Mutant prokaryotic strains, which have been obtained by non-directed mutagenesis and selection, show profound differences in their genomic DNA when compared to wild-type strains. The mutant strains have been selected based on the maximum product titer that can be obtained. As the mutant strains harbor a number of auxotrophies they cannot be used for cultivation in a chemically defined minimal growth medium. The mutant strains required the feeding of amino acids to complement their auxotrophies resulting in increased cultivation costs.
U.S. Pat. No. 5,932,439 reports Escherichia coli K-12 strains for production of recombinant proteins.